1#ifndef CEPH_CRUSH_CRUSH_H
2#define CEPH_CRUSH_CRUSH_H
3
4#include <linux/types.h>
5
6/*
7 * CRUSH is a pseudo-random data distribution algorithm that
8 * efficiently distributes input values (typically, data objects)
9 * across a heterogeneous, structured storage cluster.
10 *
11 * The algorithm was originally described in detail in this paper
12 * (although the algorithm has evolved somewhat since then):
13 *
14 *     http://www.ssrc.ucsc.edu/Papers/weil-sc06.pdf
15 *
16 * LGPL2
17 */
18
19
20#define CRUSH_MAGIC 0x00010000ul   /* for detecting algorithm revisions */
21
22#define CRUSH_MAX_DEPTH 10  /* max crush hierarchy depth */
23
24
25#define CRUSH_ITEM_UNDEF  0x7ffffffe  /* undefined result (internal use only) */
26#define CRUSH_ITEM_NONE   0x7fffffff  /* no result */
27
28/*
29 * CRUSH uses user-defined "rules" to describe how inputs should be
30 * mapped to devices.  A rule consists of sequence of steps to perform
31 * to generate the set of output devices.
32 */
33struct crush_rule_step {
34	__u32 op;
35	__s32 arg1;
36	__s32 arg2;
37};
38
39/* step op codes */
40enum {
41	CRUSH_RULE_NOOP = 0,
42	CRUSH_RULE_TAKE = 1,          /* arg1 = value to start with */
43	CRUSH_RULE_CHOOSE_FIRSTN = 2, /* arg1 = num items to pick */
44				      /* arg2 = type */
45	CRUSH_RULE_CHOOSE_INDEP = 3,  /* same */
46	CRUSH_RULE_EMIT = 4,          /* no args */
47	CRUSH_RULE_CHOOSELEAF_FIRSTN = 6,
48	CRUSH_RULE_CHOOSELEAF_INDEP = 7,
49
50	CRUSH_RULE_SET_CHOOSE_TRIES = 8, /* override choose_total_tries */
51	CRUSH_RULE_SET_CHOOSELEAF_TRIES = 9, /* override chooseleaf_descend_once */
52	CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES = 10,
53	CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES = 11,
54	CRUSH_RULE_SET_CHOOSELEAF_VARY_R = 12
55};
56
57/*
58 * for specifying choose num (arg1) relative to the max parameter
59 * passed to do_rule
60 */
61#define CRUSH_CHOOSE_N            0
62#define CRUSH_CHOOSE_N_MINUS(x)   (-(x))
63
64/*
65 * The rule mask is used to describe what the rule is intended for.
66 * Given a ruleset and size of output set, we search through the
67 * rule list for a matching rule_mask.
68 */
69struct crush_rule_mask {
70	__u8 ruleset;
71	__u8 type;
72	__u8 min_size;
73	__u8 max_size;
74};
75
76struct crush_rule {
77	__u32 len;
78	struct crush_rule_mask mask;
79	struct crush_rule_step steps[0];
80};
81
82#define crush_rule_size(len) (sizeof(struct crush_rule) + \
83			      (len)*sizeof(struct crush_rule_step))
84
85
86
87/*
88 * A bucket is a named container of other items (either devices or
89 * other buckets).  Items within a bucket are chosen using one of a
90 * few different algorithms.  The table summarizes how the speed of
91 * each option measures up against mapping stability when items are
92 * added or removed.
93 *
94 *  Bucket Alg     Speed       Additions    Removals
95 *  ------------------------------------------------
96 *  uniform         O(1)       poor         poor
97 *  list            O(n)       optimal      poor
98 *  tree            O(log n)   good         good
99 *  straw           O(n)       better       better
100 *  straw2          O(n)       optimal      optimal
101 */
102enum {
103	CRUSH_BUCKET_UNIFORM = 1,
104	CRUSH_BUCKET_LIST = 2,
105	CRUSH_BUCKET_TREE = 3,
106	CRUSH_BUCKET_STRAW = 4,
107	CRUSH_BUCKET_STRAW2 = 5,
108};
109extern const char *crush_bucket_alg_name(int alg);
110
111struct crush_bucket {
112	__s32 id;        /* this'll be negative */
113	__u16 type;      /* non-zero; type=0 is reserved for devices */
114	__u8 alg;        /* one of CRUSH_BUCKET_* */
115	__u8 hash;       /* which hash function to use, CRUSH_HASH_* */
116	__u32 weight;    /* 16-bit fixed point */
117	__u32 size;      /* num items */
118	__s32 *items;
119
120	/*
121	 * cached random permutation: used for uniform bucket and for
122	 * the linear search fallback for the other bucket types.
123	 */
124	__u32 perm_x;  /* @x for which *perm is defined */
125	__u32 perm_n;  /* num elements of *perm that are permuted/defined */
126	__u32 *perm;
127};
128
129struct crush_bucket_uniform {
130	struct crush_bucket h;
131	__u32 item_weight;  /* 16-bit fixed point; all items equally weighted */
132};
133
134struct crush_bucket_list {
135	struct crush_bucket h;
136	__u32 *item_weights;  /* 16-bit fixed point */
137	__u32 *sum_weights;   /* 16-bit fixed point.  element i is sum
138				 of weights 0..i, inclusive */
139};
140
141struct crush_bucket_tree {
142	struct crush_bucket h;  /* note: h.size is _tree_ size, not number of
143				   actual items */
144	__u8 num_nodes;
145	__u32 *node_weights;
146};
147
148struct crush_bucket_straw {
149	struct crush_bucket h;
150	__u32 *item_weights;   /* 16-bit fixed point */
151	__u32 *straws;         /* 16-bit fixed point */
152};
153
154struct crush_bucket_straw2 {
155	struct crush_bucket h;
156	__u32 *item_weights;   /* 16-bit fixed point */
157};
158
159
160
161/*
162 * CRUSH map includes all buckets, rules, etc.
163 */
164struct crush_map {
165	struct crush_bucket **buckets;
166	struct crush_rule **rules;
167
168	__s32 max_buckets;
169	__u32 max_rules;
170	__s32 max_devices;
171
172	/* choose local retries before re-descent */
173	__u32 choose_local_tries;
174	/* choose local attempts using a fallback permutation before
175	 * re-descent */
176	__u32 choose_local_fallback_tries;
177	/* choose attempts before giving up */
178	__u32 choose_total_tries;
179	/* attempt chooseleaf inner descent once for firstn mode; on
180	 * reject retry outer descent.  Note that this does *not*
181	 * apply to a collision: in that case we will retry as we used
182	 * to. */
183	__u32 chooseleaf_descend_once;
184
185	/* if non-zero, feed r into chooseleaf, bit-shifted right by (r-1)
186	 * bits.  a value of 1 is best for new clusters.  for legacy clusters
187	 * that want to limit reshuffling, a value of 3 or 4 will make the
188	 * mappings line up a bit better with previous mappings. */
189	__u8 chooseleaf_vary_r;
190};
191
192
193/* crush.c */
194extern int crush_get_bucket_item_weight(const struct crush_bucket *b, int pos);
195extern void crush_destroy_bucket_uniform(struct crush_bucket_uniform *b);
196extern void crush_destroy_bucket_list(struct crush_bucket_list *b);
197extern void crush_destroy_bucket_tree(struct crush_bucket_tree *b);
198extern void crush_destroy_bucket_straw(struct crush_bucket_straw *b);
199extern void crush_destroy_bucket_straw2(struct crush_bucket_straw2 *b);
200extern void crush_destroy_bucket(struct crush_bucket *b);
201extern void crush_destroy_rule(struct crush_rule *r);
202extern void crush_destroy(struct crush_map *map);
203
204static inline int crush_calc_tree_node(int i)
205{
206	return ((i+1) << 1)-1;
207}
208
209#endif
210